Checkpoint Therapeutics, Inc. announced the submission of a Biologics License Application (“BLA”) to the U.S. Food and Drug Administration (“FDA”) for the approval of cosibelimab, its investigational anti-PD-L1 antibody, as a treatment for patients with metastatic cutaneous squamous cell carcinoma (“cSCC”) or locally advanced cSCC who are not candidates for curative surgery or radiation. The BLA submission is based on positive efficacy and safety results from Checkpoint's ongoing registration-enabling, multi-regional, multicohort clinical trial evaluating cosibelimab administered as fixed doses of either 800 mg every two weeks or 1200 mg every three weeks in patients with selected recurrent or metastatic cancers, including pivotal cohorts in metastatic and locally advanced cSCC. In January 2022, Checkpoint announced that the metastatic cSCC cohort met its primary endpoint, with cosibelimab demonstrating a confirmed objective response rate (“ORR”) of 47.4% (95% CI: 36.0, 59.1) based on independent central review of 78 patients enrolled in the cohort using Response Evaluation Criteria in Solid Tumors version 1.1 (“RECIST 1.1”) criteria.

In June 2022, Checkpoint announced positive interim results from its locally advanced cSCC cohort, with cosibelimab demonstrating a confirmed ORR of 54.8% (95% CI: 36.0, 72.7) based on independent central review of 31 patients enrolled in the cohort, exceeding a clinically meaningful lower bound of the 95% two-sided confidence interval of 25%. Based upon interactions with the FDA, the BLA submission includes both the metastatic and locally advanced cSCC indications. Cutaneous squamous cell carcinoma is the second most common type of skin cancer in the United States, with an estimated annual incidence of approximately 1 million cases according to the Skin Cancer Foundation.

While most cases are localized tumors amenable to curative resection, approximately 40,000 cases will become advanced, and an estimated 15,000 people will die from their disease each year. In addition to being a life-threatening disease, cSCC causes significant functional morbidities and cosmetic deformities based on tumors commonly arising in the head and neck region and invading blood vessels, nerves and vital organs such as the eye or ear. Cosibelimab is a potential best-in-class, high affinity, fully-human monoclonal antibody of IgG1 subtype that directly binds to programmed death ligand-1 (“PD-L1”) and blocks the PD-L1 interaction with the programmed death receptor-1 (“PD-1”) and B7.1 receptors.

Cosibelimab's primary mechanism of action is based on the inhibition of the interaction between PD-L1 and its receptors PD-1 and B7.1, which removes the suppressive effects of PD-L1 on anti-tumor CD8+ T-cells to restore the cytotoxic T cell response. Cosibelimab is potentially differentiated from the currently marketed PD-1 and PD-L1 antibodies through sustained >99% target tumor occupancy to reactivate an antitumor immune response and the additional benefit of a functional Fc domain capable of inducing antibody-dependent cell-mediated cytotoxicity (“ADCC”) for potential enhanced efficacy in certain tumor types.